Definitions for knock-knee
Random House Webster's College Dictionary
inward curvature of the legs, causing the knees to knock together in walking.
knock-knees, the knees of a person whose legs have such curvature.
Origin of knock-knee:
knock-knee, genu valgum, tibia valga(noun)
an inward slant of the thigh
a condition in which the knees are bent in so as to touch each other in walking; inknee